Overturning of eccentric foundation

One question and my points ;
- What is the reason for designing rectangular ftg. with ecc. loading ?
- You may choose square pad with dimensions around 14 ft X 14 ft ,
- you do not need any book or reference . Just follow basic foundation design rules.




Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

I think any foundation textbook will go over eccentrically loaded foundations. You just follow that and you get a triangular bearing pressure. The idea is that the bearing pressure and applied loading results in a moment couple that resolves to zero, because it wouldn't be in equilibrium otherwise. In this case, part of the foundation might be in uplift. If it's possible, it would be nice to resize the slab to make it concentric.

This is all you need to do:
-Check if the eccentric triangular bearing pressure is okay for the soil.
-Overturning: same as retaining wall. Resisting moment versus overturning moment (lateral+gravity), with a factor of safety. (Also sliding for lateral loads.)

The footing moment and shear is same as a concentric foundation. The moment arm is slightly longer due to the eccentricity. The loading from soil onto the foundation is slightly different because it's triangular.

The textbook by Bowles has a section on it. I won't post the whole thing for copyright reasons, but here's a snippet:

I am not designing , but checking it. I have to come up with it's status of stability, that's why any calculation I make, shouldn't have any doubt. This pad has some other equipment to be installed on the space left empty. But their weight is negligible for countering overturning.